JP4704009B2 - Method for suppressing discoloration of silver product surface and product by this method - Google Patents

Description

  The present invention relates to a method for suppressing or preventing surface discoloration associated with long-term progress of silver products and a product obtained by performing a treatment according to the method.

  Silver is used for decorative items in general, with its unique color, and is used as a plating for luxury products even in cosmetic containers. However, the disadvantage of silver is that it easily discolors in the atmosphere, particularly blackening or browning in an atmosphere containing sulfur. Various methods are known for the prevention, and the following three methods are mainly mentioned.

  One is a method called chromate treatment, in which an oxidation treatment of chromate is applied to the surface of a non-treated body. In addition, a method called flash plating is a method in which a non-treated body surface is plated with a thickness of 0.1 μm or less using a material that is relatively difficult to discolor, such as rhodium or palladium. Another method is to coat the surface of the non-treated body with a resin paint such as an acrylic resin, and a typical example thereof is a technique disclosed in JP-A-2002-256454. .

  In general, the surface discoloration of silver products is suppressed or prevented by any one of the surface treatment methods. However, in the case of silver products that have been subjected to surface treatment by the above-mentioned chromate treatment or resin coating, the silver surface will turn brown or black depending on the long-term passage or storage environment, and sufficient discoloration prevention effect is not obtained Is real. In addition, in the case of silver products subjected to surface treatment by flash plating, there is a problem that the color tone is slightly changed.

JP 2002-256454 A

  The object of the present invention is to apply a silver body containing silver as a main component by a conventional coating method at a low cost, while maintaining the color tone of silver and maintaining a high degree of discoloration of the silver surface over time. It is an object of the present invention to provide a surface treatment method and a product obtained by the method.

  A silver body containing silver as a main component is subjected to a surface treatment that is transparent or translucent and that does not impair the color of silver that exhibits the ability to capture or decompose SOx, thereby browning or blackening the silver surface. A method for suppressing discoloration of the surface of a silver product, characterized by suppressing discoloration of the silver body surface over a long period of time by inhibiting SOx from reaching the silver surface, wherein the surface treatment captures SOx. It is characterized by applying a coating material to which an adsorbent is added.

Further, an inorganic oxide having a primary particle diameter of 0.1 μm or less is used as an adsorbent, and the resin coating contains 10 to 20% by weight . The inorganic oxide is at least zinc oxide or aluminum oxide. Or containing titanium oxide. In particular, an inorganic oxide such as titanium oxide has a photocatalytic activity for decomposing hydrogen sulfide, and not only captures SOx but also has excellent decomposability, and it is more advanced that SOx reaches the surface of a silver body. To suppress.

Further, the resin paint is an acrylic resin paint.

  According to the present invention, the surface treatment of the present invention can be applied to a non-treated body by a conventional general coating method, for example, spray coating method, roller coating method, dipping method, etc. There is an effect that it can be applied to a possible non-processing body at a relatively low cost. Further, unlike conventional mere coating, the amount of SOx reaching the surface of the silver body, which is a non-processed body, is significantly reduced, so that an unprecedented silver surface discoloration suppressing effect can be obtained.

  A preferred embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the layer structure of the silver product of the present invention applied to the surface of a silver body.

  As shown in FIG. 1, the present invention, for example, is plated on a surface of a 250 μm thick electroformed copper plate (1) in the order of a 1 μm thick copper plating (2) and a 2 μm thick bright nickel plating (3). The surface of the silver body (5) formed by applying silver plating (4) with a thickness of 0.1 μm is subjected to chromate treatment by electrolysis or immersion for 10 seconds on the surface, and this treated layer (6 ), And a fine powder containing an inorganic oxide such as zinc oxide, aluminum oxide, or titanium oxide having a primary particle size of 0.1 μm or less, more preferably 0.07 μm or less, as an adsorbent for capturing SOx. A clear acrylic resin coating mixed therein is applied to form a coating layer (7) preferably having a thickness of 0.2 to 10 μm.

  However, the silver body (5) is not required to be a laminated structure as described above as long as the surface of the silver body (5) is composed of a material mainly composed of silver, and is not a silver lump or silver plating. Any of silver alloys may be used. In this example, the silver surface is subjected to a chromate treatment for 10 seconds. Of course, this step is not necessarily required and may or may not be performed.

  In addition, the resin paint is an acrylic resin paint here, but is not limited thereto, and can be appropriately selected according to the application. However, if a certain degree of transparency is not ensured, the color tone of silver is impaired.

  The fine powder added to the resin coating as an adsorbent for capturing SOx contains at least a fine powder of an inorganic oxide such as zinc oxide or aluminum oxide having excellent SOx adsorption characteristics, or adsorption and decomposition. It is particularly effective to contain fine powders of inorganic oxides such as titanium oxide having excellent photocatalytic activity, but if many of these inorganic oxides have a primary particle diameter exceeding 0.1 μm, visible light Therefore, the primary particle diameter is preferably 0.1 μm or less, and therefore the average particle diameter is also preferably 0.1 μm or less. Of course, inorganic oxides such as zinc oxide, aluminum oxide, and titanium oxide may be added in combination.

  Moreover, when the thickness of the coating layer (7) is 0.2 μm or less, the amount of mixing is too small, and the effect of suppressing the amount of SOx reaching the surface of the silver body (5) is too small, conversely, it is 10 μm or more. Since the light transmittance of the coating layer (7) becomes too small and appropriate transparency cannot be secured, it is desirable that the thickness of the coating layer (8) is kept within the above-mentioned range. The amount of the fine powder added is preferably 10 to 20% by weight when the coating thickness is 1 μm, but is not necessarily limited to this due to the visible light absorption of the fine powder. In addition, when the thickness of the coating layer is thin, the amount added should be increased as appropriate.

  Although the basic configuration of the present invention is as described above, when the coating material configured as described above is applied to the non-treated body, a conventionally selected application method can be employed. FIG. 2 shows a cross section of the layer structure of the silver product obtained by performing the surface treatment for suppressing the discoloration of the silver surface.

  Further, as shown in FIG. 1, a clear acrylic resin paint having a silicon oxide powder having an average particle diameter of 10 μm added to the surface of the surface-treated silver product so as to form a mat paint layer (8) having a thickness of 5 μm. It is good also as a silver product which gave the surface finish which applied and exhibits the matte appearance. Of course, it is not always necessary to apply a clear acrylic resin coating with a thickness of 5 μm to which a 10 μm silicon oxide powder is added in order to finish the matte surface.

Sectional drawing which shows the layer structure of the silver product of the said invention given to the silver body surface

Explanation of symbols

1 Electroformed Copper Plate 2 Copper Plating 3 Bright Nickel Plating 4 Silver Plating 5 Silver Body 6 Chromate Treatment Layer 7 Paint Layer 8 Matt Paint Layer

Claims (4)

The silver body containing silver as a main component contains 10 to 20% by weight of one or more powders selected from the group consisting of zinc oxide, aluminum oxide, and titanium oxide having a primary particle size of 0.1 μm or less. A method for inhibiting discoloration of a silver product, comprising applying a resin paint to form a coating film having a thickness of 0.2 to 10 μm . The silver body containing silver as a main component contains 10 to 20% by weight of one or more powders selected from the group consisting of zinc oxide, aluminum oxide, and titanium oxide having a primary particle size of 0.1 μm or less. A silver product characterized in that a resin film is applied to form a coating film having a thickness of 0.2 to 10 μm. 2. The method for inhibiting discoloration of silver products according to claim 1, wherein the resin paint is an acrylic resin paint. The silver product according to claim 2, wherein the resin paint is an acrylic resin paint.

Images